JPS6317773B2 - - Google Patents

Description

[Detailed description of the invention] The present invention is based on the oxide superconductor BaPb _1-x Bi _x O ₃ (0.05
This relates to a method of patterning an oxide thin film containing Ba and Pb at the same time, such as x0.3).

Among oxides containing Ba, barium titanate BaTiO ₃
The etching solution is a mixture of HCl and HF, a mixture of HNO ₃ and HF, or HCl, HNO ₃ ,
A mixed solution of HF or concentrated phosphoric acid (H ₃ PO ₄ ) is used. Zircon lead titanate (Pb(ZrTi)O ₃ ) is a famous oxide containing Pb, and an aqueous solution of HF is used as an etching solution. is used.

However, there is no suitable etching solution for oxides containing both Ba and Pb, such as the superconducting oxide BaPb _1-x Bi _x O ₃ .

The BaPb _1-x Bi _x O ₃ thin film is etched with an aqueous HCl solution, but after the BaCl ₂ is eluted, the PbCl ₂ produced by the reaction with HCl remains on the edge of the thin film because it is not soluble in water, and the thin film pattern is Dimensional accuracy is not achieved.

Pb( _NO3 ) ₂ is water soluble, but BaPb1 _-x Bi _{x O3}
is almost insoluble in an aqueous solution of HNO ₃ .

The present invention aims to provide a method for forming a pattern by etching a thin film of a composite oxide containing both Ba and Pb with high dimensional accuracy without leaving any insoluble matter on the end face.

The solubility of BaCl ₂ and Ba(ClO ₄ ) ₂ in water at 25° C. is 27.1 and about 75, respectively. However, here, the solubility is the amount contained in 100g of saturated solution.
It is expressed by the weight of BaCl ₂ and Ba(ClO ₄ ) ₂ .

According to the Chemical Handbook (Basic Edition) (published by Maruzen), Pb compounds that exhibit the same level of solubility in water as BaCl ₂ and Ba(ClO ₄ ) ₂ have Pb(NO ₃ ) ₂ at 25°C.
37.73, Pb(ClO ₄ ) ₂・3H ₂ O is 81.5, Pb(SO ₃ NH ₂ ) ₂
is 710 (however, the mass number of the solute contained in the saturated solution 1), and PbSiF ₆ is 68.97 (the mass number in 100 g).

A suitable aqueous solution for preparing the latter two salts is complex and unsuitable. Furthermore, Pb easily dissolves in HNO ₃ to form Pb(NO ₃ ) ₂ , but Pb oxide hardly dissolves in HNO ₃ solution.

Therefore, assuming that Ba and Pb are commonly dissolved,
Possibly _HClO4 . However, the rate at which BaPb _1-x Bi _x O ₃ dissolves in an aqueous solution of HClO ₄ is extremely low. We discovered that by adding an appropriate amount of HCl to HClO ₄ , it was possible to etch the sides of a thin film pattern without making it cloudy.

Example 1 A HCl aqueous solution is prepared by diluting concentrated hydrochloric acid HCl (37% by weight, 12N) in water to 2% by volume. BaPb _0.75 Bi _0.35
A positive resist was applied onto a thin film of O ₃ with a thickness of 5000 Å, exposed to light, electron beams, or X-rays through a mask with a circuit pattern drawn thereon, and developed to remove unnecessary portions of the resist. After forming a pattern with the resist in this manner, the substrate was immersed in the above HCl aqueous solution for several seconds to perform etching, and then the resist was removed with acetone.

The BaPb _0.75 Bi _0.25 O ₃ thin film pattern had a line width of 50 μm, but a white high-resistance layer with a width of about 0.1 μm remained along the sides.

Example 2 Using a solution in which HClO ₄ (60.0-62.0% solution) was added to water and diluted to 50% by volume, and 1% by volume of HCl (35.0-37.0% solution) was added, the same procedure as above was carried out.
A BaPb _0.75 Bi _0.25 O ₃ thin film pattern was formed. After etching for about 7 seconds, the side surface of the thin film did not become cloudy and the etched surface was almost perpendicular to the substrate. Moreover, if the film is heated for more than 15 seconds, the top surface of the film becomes thinner than the bottom surface, and the cross section becomes trapezoidal. In addition, add 20 to 60% HClO ₄ to water by volume, and add 1 HCl to this.
Etching is preferably carried out with a solution containing ~0.3% (by volume). Note that the volume of HClO ₄ is 20 to 60
%, it is observed that the sides of the membrane become cloudy. Furthermore, if the HCl content exceeds 1%, the etching rate becomes extremely high, making operation difficult. Also 0.3%
When it is less than 100%, it is observed that the side surface of the membrane becomes cloudy.

As mentioned above, the etching solution of the present invention does not form a white high-resistance layer on the side surface of thin film wiring.
It has the effect of forming a BaPb _1-x Bi _x O ₃ pattern.

Claims (1)

[Claims] 1. HClO ₄ (60.0-62.0% solution) is added at a volume ratio of 20-60% to water, and HCl
An oxide thin film pattern forming method characterized by etching an oxide thin film containing Ba and Pb at the same time with a solution containing 1 to 0.3% by volume of (35.0 to 37.0% solution). 2 Form a BaPb _1-x Bi _x O ₃ thin film on the substrate, apply a positive resist on it, expose it to light through a mask with a circuit pattern drawn on it, develop it, and then BaPb _1-x
2. The method of forming an oxide thin film pattern according to claim 1, wherein unnecessary portions of the Bi _x O ₃ thin film are removed using the etching solution.